Relatively inexpensive novelty items containing hidden images are produced in large quantities and are used in a variety of applications including game pieces, food packaging prizes, educational children's books and the like. Many of these items contain hidden images. The images may be developed or revealed by applying a liquid or solid developer to the hidden image area of the object, by removing an opaque coating over the image, by heating the image, by rubbing the image to rupture microcapsules containing color developer or colorant and the like. The disadvantage of many of these items is that the image is often blurry, weakly developed and/or does not contain vibrant well defined colors. Another disadvantage of such objects is that the developer or solvent is often toxic or hazardous and thus could be dangerous when used by unsupervised children or infants.
Color forming dyes which are applied to a substrate in the form of microcapsules have limited application for producing images as the microcapsules are relatively fragile and care must be taken to assure that the microcapsules are applied to the substrate without substantial breakage of the microcapsules. Scuffing the printed surface or exposing the printed surface to heat may prematurely rupture the microcapsules. Thus it is difficult to print latent or hidden images using microcapsules containing the reactive components by four color process techniques. Another disadvantage of microcapsules containing the color former or developer compound is that the developed colors are somewhat diluted by the presence of the microcapsule material and are less vibrant than colors developed in the absence of microcapsules.
In addition to the use of microcapsules, chromogenic compounds have been dispersed in a wax medium and applied to a substrate. The wax medium, however, may dilute or blur the color forming compounds and delay or retard the speed the image develops. As with the microcapsules described above, scuffing or exposing the wax medium to heat may cause premature release of the color forming compounds or developer. Accordingly, there remains a need for cost effect devices and systems capable of applying color forming compounds to substrates to produce full color images having improved color vibrancy.
Considering the foregoing, the disclosure provides a latent image developing system, a novelty kit, and an ink composition for printing latent images on a substrate. The latent image developing system includes a first substrate containing a colorless image deposited on a first surface thereof. A developer component is provided that is reactive with the colorless image to provide a visible image. The developer component is selected from a developer instrument, a developer finger paint, a developer coating on a first surface of a substantially transparent substrate for adhesive attachment to the first substrate, and a combination of one or more of the developer instrument, the developer finger paint, and the developer coating. The latent image developing system optionally includes, an image blocking instrument for concealing at least a portion of the visible image. The image blocking instrument includes a blocking composition applicator and an aqueous mixture of blocking composition and water.
In another aspect the disclosure provides a novelty kit having therein a first substrate containing a colorless image deposited on a first surface thereof. A developer component is included in the novelty kit that is reactive with the colorless image to provide a visible image. The developer component selected from a developer instrument, a developer finger paint, a developer coating on a first surface of a second substrate for adhesive attachment to the first substrate, and a combination of one or more of the developer instrument, the developer finger paint, and the developer coating. An optional component of the novelty kit is an image blocking instrument for concealing at least a portion of the visible image. The image blocking instrument includes a blocking composition applicator and an aqueous mixture of blocking composition and water.
Yet another embodiment of the disclosure provides an ink composition for printing a colorless image on a first substrate. The ink composition includes a substantially colorless flexographic ink base made of a binder resin and from about 5 to about 20 percent by weight of a substantially colorless compound dissolved in a solvent portion of the ink base for printing the colorless image on the first substrate. The ink composition is reactive with a developer component selected from a developer compound dissolved in from about 35 to about 85 percent carrier fluid, a water-base developer finger paint, a developer coating on a first surface of a second substrate for adhesive attachment to the first substrate, and a combination of one or more of the developer instrument, the water-base developer finger paint, and the developer coating. The developer component is effective to provide a visible image on the first substrate when reacted with the ink composition.
An important advantage of embodiments of the disclosure is that black and white, spot color, or full color images may be developed rapidly which have excellent resolution and/or possess vibrant colors with high color intensity without having to apply relatively heavy ink coverage to a substrate to obtain the high color intensity images. Still another advantage of embodiments of the disclosure is that developer coating on the second substrate may provide images that are substantially permanent and cannot be readily altered or modified thereby improving the security of the developed images. Another advantage of the embodiments of the disclosure is that alternate method of developing an image may be used with the same latent image ink composition to provide a variety of novelty items. A further advantage of the compositions and systems described herein is that each of the components is substantially colorless until applied to a previously printed or coated substrate. Accordingly, the developer component and ink compositions may not stain or mark clothing, skin, furniture, walls or other objects. Still another advantage of the embodiments described herein is the ability to provide clandestine messages by selective blocking development of latent images on a substrate.